U.S. patent application number 15/123552 was filed with the patent office on 2017-03-16 for transparent fluorescent sialon ceramic and method of producing same.
This patent application is currently assigned to Kanagawa Academy of Science and Technology. The applicant listed for this patent is Kanagawa Academy of Science and Technology, National University Corporation YOKOHAMA National University. Invention is credited to Yuki Sano, Takuma Takahashi, Takehiko Tanaka, Junichi Tatami, Masahiro Yokouchi.
Application Number | 20170073578 15/123552 |
Document ID | / |
Family ID | 54055412 |
Filed Date | 2017-03-16 |
United States Patent
Application |
20170073578 |
Kind Code |
A1 |
Takahashi; Takuma ; et
al. |
March 16, 2017 |
TRANSPARENT FLUORESCENT SIALON CERAMIC AND METHOD OF PRODUCING
SAME
Abstract
Provided are a transparent fluorescent sialon ceramic having
fluorescence and optical transparency; and a method of producing
the same. Such a transparent fluorescent sialon ceramic includes a
sialon phosphor which contains a matrix formed of a silicon nitride
compound represented by the formula M.sub.x(Si,Ai).sub.y(N,O).sub.z
(here, M represents at least one selected from the group consisting
of Li, alkaline earth metals, and rare earth metals,
0.ltoreq.x/z<3, and 0<y/z<1) and a luminescent center
element.
Inventors: |
Takahashi; Takuma;
(Kawasaki-shi, JP) ; Tatami; Junichi;
(Yokohama-shi, JP) ; Sano; Yuki; (Yokohama-shi,
JP) ; Tanaka; Takehiko; (Yokohama-shi, JP) ;
Yokouchi; Masahiro; (Ebina-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kanagawa Academy of Science and Technology
National University Corporation YOKOHAMA National
University |
Kawasaki-shi
Yokohama-shi |
|
JP
JP |
|
|
Assignee: |
Kanagawa Academy of Science and
Technology
Kawasaki-shi
JP
National University Corporation YOKOHAMA National
University
Yokohama-shi
JP
|
Family ID: |
54055412 |
Appl. No.: |
15/123552 |
Filed: |
March 6, 2015 |
PCT Filed: |
March 6, 2015 |
PCT NO: |
PCT/JP2015/056680 |
371 Date: |
September 2, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 2235/3287 20130101;
C04B 2235/6562 20130101; C04B 2235/767 20130101; C04B 2235/5445
20130101; C04B 2235/6581 20130101; C04B 2235/5436 20130101; C04B
2235/3281 20130101; C04B 2235/9653 20130101; H01L 33/502 20130101;
C04B 2235/3284 20130101; C04B 2235/3296 20130101; C04B 2235/661
20130101; C04B 35/597 20130101; C04B 2235/3203 20130101; C04B
35/62625 20130101; C04B 2235/3873 20130101; C04B 35/6303 20130101;
C04B 2235/3418 20130101; C04B 35/6455 20130101; C04B 2235/3289
20130101; C04B 2235/3229 20130101; C09K 11/0883 20130101; C04B
2235/3293 20130101; C04B 2235/666 20130101; C04B 2235/6586
20130101; C04B 2235/3286 20130101; C04B 2235/9646 20130101; C04B
35/645 20130101; C04B 2235/3201 20130101; C04B 2235/3241 20130101;
C09K 11/7774 20130101; C04B 2235/604 20130101; C04B 2235/3224
20130101; C04B 2235/658 20130101; C04B 2235/3294 20130101; C04B
2235/3205 20130101; C04B 2235/3244 20130101; C04B 2235/3272
20130101; C09K 11/7721 20130101; C09K 11/7792 20130101; C04B 35/638
20130101; C04B 2235/3217 20130101; C04B 2235/3291 20130101; C04B
2235/3865 20130101; C04B 2235/3225 20130101; C04B 2235/3298
20130101; C09K 11/025 20130101; C04B 2235/3262 20130101; C04B
2235/766 20130101; C09K 11/7734 20130101; C04B 35/62695
20130101 |
International
Class: |
C09K 11/77 20060101
C09K011/77; C04B 35/63 20060101 C04B035/63; C04B 35/597 20060101
C04B035/597; C04B 35/645 20060101 C04B035/645; C09K 11/02 20060101
C09K011/02; C09K 11/08 20060101 C09K011/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2014 |
JP |
2014-044430 |
Claims
1. A transparent fluorescent sialon ceramic comprising: a sialon
phosphor which contains a matrix formed of a silicon nitride
compound represented by the formula M.sub.x(Si,Al).sub.y(N,O).sub.z
wherein M represents at least one member selected from the group
consisting of Li, alkaline earth metals, and rare earth metals,
0.ltoreq.x/z<3, and 0<y/z<1 and a luminescent center
element.
2. The transparent fluorescent sialon ceramic according to claim 1,
wherein the silicon nitride compound is .beta.-sialon represented
by the formula (Si,Al).sub.6(N,O).sub.8.
3. The transparent fluorescent sialon ceramic according to claim 1,
wherein the silicon nitride compound is .alpha.-sialon represented
by the formula M.sub.x(Si,Al).sub.12(N,O).sub.16 wherein M
represents at least one member selected from the group consisting
of Li, alkaline earth metals, and rare earth metals, and
0.3.ltoreq.x.ltoreq.2.
4. The transparent fluorescent sialon ceramic according to claim 1,
wherein the silicon nitride compound is a compound which is
represented by the formula M.sub.x(Si,Al).sub.y(N,O).sub.z wherein
M represents at least one member selected from the group consisting
of alkaline earth metals and rare earth metals,
0.2.ltoreq.x/z.ltoreq.0.6, and 0.4.ltoreq.y/z.ltoreq.0.8 and has a
crystal structure similar to a wurtzite type crystal structure.
5. The transparent fluorescent sialon ceramic according to claim 1,
wherein the luminescent center element is selected from the group
consisting of Eu, Ce, Mn, Tb, Yb, Dy, Sm, Tm, Pr, Nd, Pm, Ho, Er,
Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In, Sb, Au, Hg, Tl, Pb, Bi,
and Fe.
6. A method of producing a transparent fluorescent sialon ceramic
comprising: preparing a primary molded body by uniaxial press
molding of a mixture which contains at least silicon nitride
powder, a substance serving as a luminescent center element source,
and a sintering aid; preparing a secondary molded body by cold
isostatic press molding of the primary molded body; preparing a
sintered body by pre-sintering the secondary molded body in a
nitrogen atmosphere; and performing a pressure-sintering treatment
on the sintered body in a nitrogen atmosphere.
7. A method of producing a transparent fluorescent sialon ceramic
comprising: performing a pressure-sintering treatment on a mixture
which contains at least silicon nitride powder, a substance serving
as a luminescent center element source, and a sintering aid under a
nitrogen atmosphere.
8. The method of producing a transparent fluorescent sialon ceramic
according to claim 6, wherein at least one member selected from the
group consisting of rare earth oxides, alkaline earth metal oxides,
aluminum oxide, aluminum nitride, silicon oxide, and hafnium oxide
is used as the sintering aid.
9. The transparent fluorescent sialon ceramic according to claim 2,
wherein the luminescent center element is selected from the group
consisting of Eu, Ce, Mn, Tb, Yb, Dy, Sm, Tm, Pr, Nd, Pm, Ho, Er,
Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In, Sb, Au, Hg, Tl, Pb, Bi,
and Fe.
10. The transparent fluorescent sialon ceramic according to claim
3, wherein the luminescent center element is selected from the
group consisting of Eu, Ce, Mn, Tb, Yb, Dy, Sm, Tm, Pr, Nd, Pm, Ho,
Er, Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In, Sb, Au, Hg, Tl, Pb,
Bi, and Fe.
11. The transparent fluorescent sialon ceramic according to claim
4, wherein the luminescent center element is selected from the
group consisting of Eu, Ce, Mn, Tb, Yb, Dy, Sm, Tm, Pr, Nd, Pm, Ho,
Er, Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In, Sb, Au, Hg, Tl, Pb,
Bi, and Fe.
12. The method of producing a transparent fluorescent sialon
ceramic according to claim 7, wherein at least one member selected
from the group consisting of rare earth oxides, alkaline earth
metal oxides, aluminum oxide, aluminum nitride, silicon oxide, and
hafnium oxide is used as the sintering aid.
Description
TECHNICAL FIELD
[0001] The present invention relates to a transparent fluorescent
sialon ceramic and a method of producing the same.
[0002] Priority is claimed on Japanese Patent Application No.
2014-044430, filed Mar. 6, 2014, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] In recent years, blue light-emitting diodes (LED) have come
into practical use and white LEDs using these blue LEDs have been
developed. Since white LEDs have lower power consumption than white
light sources of the related art and have a long lifetime, white
LEDs are used for backlights for liquid crystal display devices and
indoor and outdoor lighting equipment.
[0004] For example, a white LED is obtained by coating the surface
of a blue LED with a phosphor or the like (for example, see PTL
1).
CITATION LIST
Patent Literature
[0005] [PTL 1] Japanese Unexamined Patent Application, First
Publication No. 2013-173868
SUMMARY OF INVENTION
Technical Problem
[0006] Since the above-described nitride ceramic phosphor is
powdery, the nitride ceramic phosphor is dispersed in a
light-transmitting resin and fixed to the surface of a blue LED. In
this case, the luminous efficiency of a white LED is degraded due
to scattering of light caused by a difference in refractive index
between the nitride ceramic phosphor and the resin.
[0007] It is considered that such a problem can be solved by
obtaining a transparent mass (bulk body) formed of only a nitride
ceramic phosphor. In order to make the nitride ceramic phosphor
transparent, it is necessary to promote sintering of raw material
powder of the nitride ceramic phosphor and to remove pores which
are present in a sintered body and become sources of scattered
light. Further, since the nitride ceramic phosphor has a high
refractive index, the transparency is degraded when a glass phase
with a low refractive index remains after firing. However, a method
of removing pores from a nitride ceramic phosphor and a method of
preventing a glass phase from remaining on the nitride ceramic
phosphor have not been established.
[0008] The present invention has been made in consideration of the
above-described circumstances, and an object thereof is to provide
a transparent fluorescent sialon ceramic having fluorescence and
light-transmitting properties and a method of producing the
same.
Solution to Problem
[0009] [1] According to one aspect of the present invention, there
is provided a transparent fluorescent sialon ceramic including: a
sialon phosphor which contains a matrix formed of a silicon nitride
compound represented by the formula M.sub.x(Si,Al).sub.y(N,O).sub.z
(here, M represents at least one selected from the group consisting
of Li, alkaline earth metals, and rare earth metals,
0.ltoreq.x/z<3, and 0<y/z<1) and a luminescent center
element.
[0010] [2] In the transparent fluorescent sialon ceramic according
to [1], the silicon nitride compound may be .beta.-sialon
represented by the formula (Si,Al).sub.6(N,O).sub.8.
[0011] [3] In the transparent fluorescent sialon ceramic according
to [1], the silicon nitride compound may be .alpha.-sialon
represented by the formula M.sub.x(Si,Al).sub.12(N,O).sub.16 (here,
M represents at least one selected from the group consisting of Li,
alkaline earth metals, and rare earth metals, and
0.3.ltoreq.x.ltoreq.2).
[0012] [4] In the transparent fluorescent sialon ceramic according
to [1], the silicon nitride compound may be a compound which is
represented by the formula M.sub.x(Si,Al).sub.y(N,O).sub.z (here, M
represents at least one selected from the group consisting of
alkaline earth metals and rare earth metals,
0.2.ltoreq.x/z.ltoreq.0.6, and 0.4.ltoreq.y/z.ltoreq.0.8) and has a
crystal structure similar to a wurtzite type crystal structure.
[0013] [5] In the transparent fluorescent sialon ceramic according
to any one of [1] to [4], the luminescent center element may be one
selected from the group consisting of Eu, Ce, Mn, Tb, Yb, Dy, Sm,
Tm, Pr, Nd, Pm, Ho, Er, Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In,
Sb, Au, Hg, Tl, Pb, Bi, and Fe.
[0014] [6] According to another aspect of the present invention,
there is provided a method of producing a transparent fluorescent
sialon ceramic including: a process of preparing a primary molded
body by uniaxial press molding of a mixture which contains at least
silicon nitride powder, a substance serving as a luminescent center
element source, and a sintering aid; a process of preparing a
secondary molded body by cold isostatic press molding of the
primary molded body; a process of preparing a sintered body by
pre-sintering the secondary molded body in a nitrogen atmosphere;
and a process of performing a pressure-sintering treatment to the
sintered body on a nitrogen atmosphere. Here, the pre-sintering
indicates densifying of the secondary molded body (sintered body)
at 0.1 MPa to 1 MPa in a nitrogen atmosphere before pressure
sintering. Further, the pressure sintering is a sintering method
typified by hot isostatic pressure sintering (HIP sintering), spark
plasma sintering (SPS), or a hot press sintering (HP
sintering).
[0015] [7] According to still another aspect of the present
invention, there is provided a method of producing a transparent
fluorescent sialon ceramic including: a process of performing a
pressure-sintering treatment on a mixture which contains at least
silicon nitride powder, a substance serving as a luminescent center
element source, and a sintering aid under a nitrogen
atmosphere.
[0016] [8] In the method of producing a transparent fluorescent
sialon ceramic according to [6] or [7], at least one selected from
the group consisting of rare earth oxides, alkaline earth metal
oxides, aluminum oxide, aluminum nitride, silicon oxide, and
hafnium oxide may be used as the sintering aid.
Advantageous Effects of Invention
[0017] According to the present invention, it is possible to mold a
transparent fluorescent sialon ceramic into a predetermined shape
with the form as it is and to apply the molded transparent
fluorescent sialon ceramic to a white LED. Further, it is not
necessary for a sialon phosphor to be dispersed in a resin for use
as in the related art, and it is possible to obtain a transparent
fluorescent sialon ceramic in which the luminous efficiency of a
white LED is not degraded due to scattering of light caused by a
difference in refractive index between a sialon phosphor and a
resin.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a graph showing measurement results of
transmittances of visible light in transparent fluorescent sialon
ceramics of Experiment Examples 1 to 4.
[0019] FIG. 2 is a graph showing measurement results of an emission
spectrum and an excitation spectrum in the transparent fluorescent
sialon ceramic of Experiment Example 1.
[0020] FIG. 3 is a graph showing measurement results of an emission
spectrum and an excitation spectrum in the transparent fluorescent
sialon ceramic of Experiment Example 2.
[0021] FIG. 4 is a graph showing measurement results of an emission
spectrum and an excitation spectrum in the transparent fluorescent
sialon ceramic of Experiment Example 3.
[0022] FIG. 5 is a graph showing measurement results of an emission
spectrum and an excitation spectrum in the transparent fluorescent
sialon ceramic of Experiment Example 4.
[0023] FIG. 6 is a graph showing measurement results of
transmittances of visible light in transparent fluorescent sialon
ceramics of Experiment Examples 5 to 9.
[0024] FIG. 7 is a graph showing measurement results of an emission
spectrum in transparent fluorescent sialon ceramics of Experiment
Examples 6 and 10.
[0025] FIG. 8 is a graph showing a measurement result of an
excitation spectrum in the transparent fluorescent sialon ceramic
of Experiment Example 6.
[0026] FIG. 9 is a graph showing a measurement result of an
excitation spectrum in a transparent fluorescent sialon ceramic of
Experiment Example 12.
[0027] FIG. 10 is a graph showing a measurement result of an
excitation spectrum in a transparent fluorescent sialon ceramic of
Experiment Example 13.
DESCRIPTION OF EMBODIMENTS
[0028] Embodiments of a transparent fluorescent sialon ceramic of
the present invention and a method of producing the same will be
described.
[0029] Further, the embodiments will be described in detail for
better understanding of the scope of the invention and are not
intended to limit the present invention unless otherwise noted.
[0030] [Transparent Fluorescent Sialon Ceramic]
[0031] The transparent fluorescent sialon ceramic of the present
embodiment includes a sialon phosphor which contains a matrix
formed of a silicon nitride compound represented by the formula
M.sub.x(Si,Al).sub.y(N,O).sub.z (here, M represents at least one
selected from the group consisting of Li, alkaline earth metals,
and rare earth metals, 0.ltoreq.x/z<3, and 0<y/z<1) and a
luminescent center element.
[0032] That is, the transparent fluorescent sialon ceramic of the
present embodiment includes a sialon phosphor which contains a
matrix formed of a silicon nitride compound represented by the
formula M.sub.x(Si,Al).sub.y(N,O).sub.z (here, M represents at
least one selected from the group consisting of Li, alkaline earth
metals, and rare earth metals, 0.ltoreq.x/z<3, and
0<y/z<1) and a luminescent center element included (present)
in the matrix.
[0033] The transparent fluorescent sialon ceramic of the present
embodiment is a sintered body formed by sintering a raw material
containing silicon nitride powder as described below. The
transparent fluorescent sialon ceramic is not particulate
(powdery), and is a polycrystalline body formed by aggregating
plural single crystals of a sialon phosphor and is also a sintered
body having an arbitrary shape. The shape of the sintered body is
not particularly limited, and examples thereof include a
disc-shape, a flat shape, a convex lens shape, a concave lens
shape, a spherical shape, a hemispherical shape, a cubic shape, a
rectangular parallelepiped shape, a columnar shape such as a prism
or a column, and a tubular shape such as a square tube or a
cylinder.
[0034] For example, in a case where the transparent fluorescent
sialon ceramic of the present embodiment is applied to a white LED,
the transparent fluorescent sialon ceramic is formed in a shape of
covering the outer periphery of a blue LED serving as a light
source and then used.
[0035] The term "transparent" in the transparent fluorescent sialon
ceramic of the present embodiment indicates that the linear
transmittance at a wavelength of 800 nm is 10% or greater.
[0036] In the formula M.sub.x(Si,Al).sub.y(N,O).sub.z, in a case
where x represents 0, y represents 6, and z represents 8, the
silicon nitride compound is .beta.-sialon represented by the
formula (Si,Al).sub.6(N,O).sub.8. In a case where y represents 12
and z represents 16, the silicon nitride compound is .alpha.-sialon
represented by the formula M.sub.x(Si,Al).sub.12(N,O).sub.16 (here,
M represents at least one selected from the group consisting of Li,
alkaline earth metals, and rare earth metals, and
0.3.ltoreq.x.ltoreq.2). In a case where M represents Ca, x
represents 1, y represents 1, and z represents 2, the silicon
nitride compound is CaSiN.sub.2. In a case where M represents Ca, x
represents 2, y represents 5, and z represents 8, the silicon
nitride compound is Ca.sub.2Si.sub.5N.sub.8. In a case where M
represents Sr, x represents 1, y represents 28, and z represents
32, the silicon nitride compound is SrSi.sub.9Al.sub.19ON.sub.31.
In a case where M represents Y, x represents 5, y represents 3, and
z represents 13, the silicon nitride compound is
Y.sub.5Si.sub.3O.sub.12N. In a case where M represents Si, x
represents 5, y represents 26, and z represents 37, the silicon
nitride compound is Si.sub.5Al.sub.5Si.sub.21N.sub.35O.sub.2.
[0037] The formula (Si,Al).sub.6(N,O).sub.8 representing
.beta.-sialon is also expressed as the formula
Si.sub.6-zAl.sub.zO.sub.zN.sub.8-z (here, 0 z 4.2).
[0038] In the formula Si.sub.6-zAl.sub.zO.sub.zN.sub.8-z, z is
preferably in a range of 0 to 1 and more preferably in a range of
0.01 to 0.5.
[0039] The formula M.sub.x(Si,Al).sub.12(N,O).sub.16 representing
.alpha.-sialon is also expressed as the formula
M.sub.xSi.sub.12-(b+c)Al.sub.(b+c)O.sub.cN.sub.16-c (here, M
represents at least one selected from the group consisting of Li,
alkaline earth metals, and rare earth metals,
0.3.ltoreq.x.ltoreq.2, 3.60.ltoreq.b.ltoreq.5.50, and
0.ltoreq.c.ltoreq.0.30).
[0040] In the formula
M.sub.xSi.sub.12-(b+)Al.sub.(b+c)O.sub.cN.sub.16-c, x is preferably
in a range of 0.5 to 2. Moreover, in the formula
M.sub.xSi.sub.12-(b+c)Al.sub.(b+c)O.sub.cN.sub.16-c, b/c is
preferably 1.5 or greater.
[0041] In addition, in the formula M.sub.x(Si,Al).sub.y(N,O).sub.z,
x/z is preferably in a range of 0.2 to 0.6 and y/z is preferably in
a range of 0.4 to 0.8. In a case where x represents 01, y
represents 1, and z represents 3, the silicon nitride compound is
CaAlSiN.sub.3.
[0042] In the present embodiment, the silicon nitride compound
represented by the formula M.sub.x(Si,Al).sub.y(N,O).sub.z is not
particularly limited, and any compound can be used as the silicon
nitride compound as long as the silicon nitride compound is a
compound which emits fluorescence and has light-transmitting
properties in a state of containing a luminescent center element by
activating the luminescent center element.
[0043] As the luminescent center element, one selected from the
group consisting of Eu, Ce, Mn, Tb, Yb, Dy, Sm, Tm, Pr, Nd, Pm, Ho,
Er, Gd, Cr, Sn, Cu, Zn, Ga, Ge, As, Ag, Cd, In, Sb, Au, Hg, Tl, Pb,
Bi, and Fe is used.
[0044] Examples of the metal element M include Li, Ca, Sr, Ba, Y,
and lanthanide metals (excluding Ce and La).
[0045] The transparent fluorescent sialon ceramic of the present
embodiment can emit various fluorescent colors by adjusting the
combination of the silicon nitride compound and the luminescent
center element. Moreover, the wavelength of light transmitted
through the transparent fluorescent sialon ceramic of the present
embodiment can be adjusted by combining the silicon nitride
compound and the luminescent center element. In this manner, the
color tone of the transparent fluorescent sialon ceramic of the
present embodiment can be adjusted.
[0046] In the transparent fluorescent sialon ceramic of the present
embodiment, in a case where the silicon nitride compound is
.beta.-sialon activated by Eu, the linear transmittance of visible
light is 11% or greater at a wavelength of 800 nm and the
fluorescent color which can be emitted is green when the thickness
of .beta.-sialon is 100 .mu.m.
[0047] Further, in a case where the silicon nitride compound is
Y-.alpha.-sialon activated by Ce, the linear transmittance of
visible light is 65% or greater at a wavelength of 800 nm and the
fluorescent color which can be emitted is blue to blue-green when
the thickness of Y-.alpha.-sialon is 100 .mu.m.
[0048] Further, in a case where the silicon nitride compound is
Ca-.alpha.-sialon activated by Eu, the linear transmittance of
visible light is 65% or greater at a wavelength of 800 nm and the
fluorescent color which can be emitted is yellow when the thickness
of Ca-.alpha.-sialon is 100 .mu.m.
[0049] Furthermore, in a case where the silicon nitride compound is
CaAlSiN.sub.3 activated by Eu, the linear transmittance of visible
light is 19% or greater at a wavelength of 800 nm and the
fluorescent color which can be emitted is red when the thickness of
CaAlSiN.sub.3 is 100 .mu.m.
[0050] In addition, the transparent fluorescent sialon ceramic of
the present embodiment is a mass formed of a sialon phosphor
containing a matrix formed of a silicon nitride compound and a
luminescent center element and can be molded into a predetermined
shape with the form as it is and applied to a white LED. Therefore,
since it is not necessary for a sialon phosphor to be dispersed in
a resin for use as in the related art, the luminous efficiency of a
white LED is not degraded due to scattering of light caused by a
difference in refractive index between a sialon phosphor and a
resin.
[0051] Moreover, since the sialon phosphor is uniformly present
throughout the entire transparent fluorescent sialon ceramic of the
present embodiment, fluorescence is emitted uniformly without being
biased and the transmittance of visible light is uniform without
being biased.
[0052] Further, the transparent fluorescent sialon ceramic of the
present embodiment has less pores or glass phases in the inside
because the transparent fluorescent sialon ceramic is produced
according to the production method described below, and thus the
degradation of transparency resulting from the pores or the glass
phases is small and light-transmitting properties are
excellent.
[0053] [Method of Producing Transparent Fluorescent Sialon
Ceramic]
[0054] The method of producing a transparent fluorescent sialon
ceramic of the present embodiment includes a process of preparing a
primary molded body by uniaxial press molding of a mixture which
contains at least silicon nitride powder, a substance serving as a
luminescent center element source, and a sintering aid; a process
of preparing a secondary molded body by cold isostatic press
molding of the primary molded body; and a process of preparing a
sintered body by gas pressure sintering of the secondary molded
body in a nitrogen atmosphere.
[0055] The method of producing a transparent fluorescent sialon
ceramic of the present embodiment is applied to a case where the
silicon nitride compound is .beta.-sialon and a case where the
silicon nitride compound is .alpha.-sialon.
[0056] Hereinafter, the method of producing the transparent
fluorescent sialon ceramic of the present embodiment will be
described by separating the case where the silicon nitride compound
is .beta.-sialon from the case where the silicon nitride compound
is .alpha.-sialon.
[0057] [Case where Silicon Nitride Compound is .beta.-Sialon]
[0058] First, a mixture of silicon nitride (Si.sub.3N.sub.4)
powder, aluminum oxide (Al.sub.2O.sub.3) powder, aluminum nitride
(AlN) powder, a substance serving as a luminescent center element
source, and a sintering aid is weighed so as to have a
predetermined mass ratio.
[0059] As the substance serving as a luminescent center element
source, europium (II) oxide (EuO), europium (III) oxide
(Eu.sub.2O.sub.3), or europium nitride (EuN) is used, for example,
in a case where the luminescent center element is Eu.
[0060] As the sintering aid, at least one selected from the group
consisting of rare earth oxides, alkaline earth metal oxides,
aluminum oxide, aluminum nitride, silicon oxide, and hafnium oxide
is used, but it is preferable to use a combination of hafnium oxide
(HfO.sub.2) and yttrium (III) oxide (Y.sub.2O.sub.3).
[0061] The mixing ratio of the above-described raw material powder
is appropriately adjusted according to the fluorescence and light
transmitting properties of the target transparent fluorescent
sialon ceramic.
[0062] Next, a dispersant is added to the raw material powder, wet
mixing is performed in ethanol using a ball mill, thereby preparing
a slurry containing raw material powder.
[0063] Subsequently, the obtained slurry is heated using a heater
such as a mantle heater and ethanol contained in the slurry is
sufficiently evaporated, thereby obtaining a mixture of raw
material powder (mixed powder).
[0064] Next, two or more sieves with meshes having sizes different
from each other are used in a stepwise manner, the above-described
mixed powder is forcedly passed through these sieves, and the mixed
powder having a predetermined particle diameter is granulated.
[0065] Subsequently, a sufficiently melted binder such as paraffin,
a lubricant such as bis(2-ethylhexyl)phthalate, and a solvent such
as cyclohexane are sufficiently stirred and mixed with each other,
thereby preparing a binder solution.
[0066] Next, the granulated mixed powder is added to the binder
solution, the binder solution is mixed into the entire mixed powder
such that the binder solution permeates into the entire mixed
powder, the mixture is heated, and then the solvent is
evaporated.
[0067] Subsequently, after the solvent is sufficiently evaporated,
the mixed powder is forcedly passed through a sieve with meshes
having a predetermined size and then granulated powder having a
predetermined particle diameter is obtained.
[0068] Next, a predetermined amount of granulated powder is
collected such that the thickness of a molded body after molding
using a mold becomes a predetermined size and then the granulated
powder is supplied into the mold.
[0069] Subsequently, uniaxial press molding is performed at a
pressure of 25 MPa to 50 MPa for 30 seconds using a uniaxial press
molding machine, thereby obtaining a primary molded body.
[0070] Next, the obtained primary molded body is chamfered and
packed in a vacuum pack.
[0071] Subsequently, the primary molded body packed in a vacuum
pack is molded by cold isostatic pressing (CIP) once or repeatedly
ten times at a pressure of 200 MPa for 1 minute using a cold
isostatic pressing device, thereby obtaining a secondary molded
body.
[0072] Next, the secondary molded body is placed on an alumina
boat, heated in an air stream of 70 L/min using an annular
resistance furnace, and degreased, and a binder included in the
secondary molded body is removed. In the degreasing process, the
heating temperature and the heating time of the secondary molded
body are set in two stages. In the first stage of heating, the
heating temperature is set to 250.degree. C. and the heating time
is set to 3 hours. In the second stage of heating, the heating
temperature is set to 500.degree. C. and the heating time is set to
3 hours.
[0073] Moreover, in order to promote evaporation of a binder or a
lubricant included in the secondary molded body to some extent or
to prevent carbon from remaining due to thermal decomposition of
the binder or the lubricant, it is preferable that the heating
temperature of the secondary molded body is set to be in a range of
300.degree. C. to 600.degree. C. and the heating time thereof is
set to be in a range of 1 hour to 10 hours.
[0074] Next, the degreased secondary molded body is pre-sintered in
a nitrogen atmosphere using a multi-purpose high-temperature
sintering furnace, thereby obtaining a sintered body.
[0075] In order to sinter the secondary molded body, a porous
crucible made of Si.sub.3N.sub.4, which is prepared by reaction
sintering, is disposed in a housing made of carbon, a porous column
plate made of Si.sub.3N.sub.4 is disposed in the crucible, and the
secondary molded body is disposed in the column plate shape.
[0076] In this sintering process, the temperature is increased at
20.degree. C./min in a vacuum (6.7.times.10.sup.-2 Pa or less) in a
temperature range of room temperature to 1200.degree. C., the
secondary molded body is pressed by nitrogen gas up to 0.25 MPa at
1200.degree. C. and pressed with a nitrogen gas flow of 4 L/min up
to 0.9 MPa while the temperature is increased at 10.degree. C./min
until the temperature reaches the target sintering temperature from
1200.degree. C. The sintering temperature of the secondary molded
body is set to be in a range of 1600.degree. C. to 1900.degree. C.
and the sintering time is set to 2 hours. Further, the pressure at
the time of sintering is set to be in a range of 0.88 MPa to 0.91
MPa in a nitrogen atmosphere.
[0077] Next, after the sintering is finished, the sintered body is
left to be naturally cooled to room temperature and then
cooled.
[0078] Subsequently, the sintered body is subjected to a
pressure-sintering treatment at a pressure of 50 MPa to 200 MPa and
a temperature of 1700.degree. C. to 1800.degree. C. for 1 hour in a
nitrogen atmosphere using a hot isostatic pressing (HIP)
device.
[0079] In this manner, the transparent fluorescent sialon ceramic
of the present embodiment is obtained.
[0080] According to the method of producing the transparent
fluorescent sialon ceramic of the present embodiment, it is
possible to remove a region having a different refractive index and
serving as a source of scattered light and a glass phase serving as
a light absorbing source by performing a process of preparing a
secondary molded body by cold isostatic press molding of the
primary molded body; a process of preparing a sintered body by
pre-sintering the secondary molded body in a nitrogen atmosphere;
and a process of performing a pressure-sintering treatment on the
sintered body in a nitrogen atmosphere. As a result, since the
sialon phosphor is uniformly present throughout the entire obtained
transparent fluorescent sialon ceramic, fluorescence is emitted
uniformly without being biased and the transmittance of visible
light is uniform without being biased. Further, the transparent
fluorescent sialon ceramic has less pores or glass phases in the
inside and thus there is no degradation of transparency resulting
from the pores or the glass phases and light-transmitting
properties are excellent. Particularly, the effect of removing
pores and glass phases is improved by means of using hafnium oxide
(HfO.sub.2) having a refractive index close to that of
.beta.-sialon, in addition to yttrium (III) oxide (Y.sub.2O.sub.3),
as a sintering aid and thus a transparent fluorescent sialon
ceramic having more excellent light transmitting properties is
obtained.
[0081] [Case where Silicon Nitride Compound is
Y-.alpha.-Sialon]
[0082] First, a mixture of silicon nitride (Si.sub.3N.sub.4)
powder, aluminum nitride (AlN) powder, a substance serving as a
luminescent center element source, and a sintering aid is weighed
so as to have a predetermined mass ratio.
[0083] As the substance serving as a luminescent center element
source, cerium (IV) oxide (CeO.sub.2) is used, for example, in a
case where the luminescent center element is Ce.
[0084] As the sintering aid, at least one selected from the group
consisting of rare earth oxides, alkaline earth metal oxides,
aluminum oxide, aluminum nitride, and silicon oxide is used, but it
is preferable to use a combination of aluminum nitride (AlN) and
yttrium (III) oxide (Y.sub.2O.sub.3).
[0085] The mixing ratio of the above-described raw material powder
is appropriately adjusted according to the fluorescence and light
transmitting properties of the target transparent fluorescent
sialon ceramic.
[0086] Next, a dispersant is added to the raw material powder, wet
mixing is performed in ethanol using a ball mill, thereby preparing
a slurry containing raw material powder.
[0087] Subsequently, the obtained slurry is heated using a heater
such as a mantle heater and ethanol contained in the slurry is
sufficiently evaporated, thereby obtaining a mixture of raw
material powder (mixed powder).
[0088] Next, two or more sieves with meshes having sizes different
from each other are used in a stepwise manner, the above-described
mixed powder is forcedly passed through these sieves, and the mixed
powder having a predetermined particle diameter is granulated.
[0089] Subsequently, a sufficiently melted binder such as paraffin,
a lubricant such as bis(2-ethylhexyl)phthalate, and a solvent such
as cyclohexane are sufficiently stirred and mixed with each other,
thereby preparing a binder solution.
[0090] Next, the granulated mixed powder is added to the binder
solution, the binder solution is mixed into the entire mixed powder
such that the binder solution permeates into the entire mixed
powder, the mixture is heated, and then the solvent is
evaporated.
[0091] Subsequently, after the solvent is sufficiently evaporated,
the mixed powder is forcedly passed through a sieve with meshes
having a predetermined size and then granulated powder having a
predetermined particle diameter is obtained.
[0092] Next, a predetermined amount of granulated powder is
collected such that the thickness of a molded body after molding
using a mold becomes a predetermined size and then the granulated
powder is supplied into the mold.
[0093] Subsequently, uniaxial press molding is performed at a
pressure of 50 MPa for 30 seconds using a uniaxial press molding
machine, thereby obtaining a primary molded body.
[0094] Next, the obtained primary molded body is chamfered and
packed in a vacuum pack.
[0095] Subsequently, the primary molded body packed in a vacuum
pack is molded by cold isostatic pressing (CIP) once or repeatedly
ten times at a pressure of 200 MPa for 1 minute using a cold
isostatic pressing device, thereby obtaining a secondary molded
body.
[0096] Next, the secondary molded body is placed on an alumina
boat, heated in an air stream of 70 L/min using an annular
resistance furnace, and degreased, and a binder included in the
secondary molded body is removed. In the degreasing process, the
heating temperature and the heating time of the secondary molded
body are set in two stages. In the first stage of heating, the
heating temperature is set to 500.degree. C. and the heating time
is set to 3 hours. In the second stage of heating, the heating
temperature is set to 560.degree. C. and the heating time is set to
3 hours.
[0097] Moreover, in order to promote evaporation of a binder or a
lubricant included in the secondary molded body to some extent or
to prevent carbon from remaining due to thermal decomposition of
the binder or the lubricant, it is preferable that the heating
temperature of the secondary molded body is set to be in a range of
300.degree. C. to 600.degree. C. and the heating time thereof is
set to be in a range of 1 hour to 10 hours.
[0098] Next, the degreased secondary molded body is pre-sintered in
a nitrogen atmosphere using a multi-purpose high-temperature
sintering furnace, thereby obtaining a sintered body.
[0099] In order to sinter the secondary molded body, a porous
crucible made of Si.sub.3N.sub.4, which is prepared by reaction
sintering, is disposed in a housing made of carbon, a porous column
plate made of Si.sub.3N.sub.4 is disposed in the crucible, and the
secondary molded body is disposed in the column plate shape.
[0100] In this sintering process, the temperature is increased at
20.degree. C./min in a vacuum (6.7.times.10.sup.-2 Pa or less) in a
temperature range of room temperature to 1200.degree. C., the
secondary molded body is pressed by nitrogen gas up to 0.25 MPa at
1200.degree. C. and pressed with a nitrogen gas flow of 4 L/min up
to 0.9 MPa while the temperature is increased at 10.degree. C./min
until the temperature reaches the target sintering temperature from
1200.degree. C. The sintering temperature of the secondary molded
body is set to 1600.degree. C. and the sintering time is set to 2
hours. Further, the pressure at the time of sintering is set to be
in a range of 0.88 MPa to 0.91 MPa in a nitrogen atmosphere.
[0101] Next, after the sintering is finished, the sintered body is
left to be naturally cooled to room temperature and then
cooled.
[0102] Subsequently, the sintered body is subjected to a
pressure-sintering treatment at a pressure of 50 MPa to 200 MPa and
a temperature of 1600.degree. C. to 1800.degree. C. for 1 hour in a
nitrogen atmosphere using a hot isostatic pressing (HIP)
device.
[0103] In this manner, the transparent fluorescent sialon ceramic
of the present embodiment is obtained.
[0104] According to the method of producing the transparent
fluorescent sialon ceramic of the present embodiment, it is
possible to remove a region having a different refractive index and
serving as a source of scattered light and a glass phase serving as
a light absorbing source by performing a process of preparing a
secondary molded body by cold isostatic press molding of the
primary molded body; a process of preparing a sintered body by
pre-sintering the secondary molded body in a nitrogen atmosphere;
and a process of performing a pressure-sintering treatment on the
sintered body in a nitrogen atmosphere. As a result, since the
sialon phosphor is uniformly present throughout the entire obtained
transparent fluorescent sialon ceramic, fluorescence is emitted
uniformly without being biased and the transmittance of visible
light is uniform without being biased. Further, the transparent
fluorescent sialon ceramic has less pores or glass phases in the
inside and thus there is no degradation of transparency resulting
from the pores or the glass phases and light-transmitting
properties are excellent.
[0105] [Case where Silicon Nitride Compound is
Ca-.alpha.-Sialon]
[0106] First, a mixture of silicon nitride (Si.sub.3N.sub.4)
powder, aluminum nitride (AlN) powder, a substance serving as a
luminescent center element source, and a sintering aid is weighed
so as to have a predetermined mass ratio.
[0107] As the substance serving as a luminescent center element
source, europium (III) oxide (Eu.sub.2O.sub.3) is used, for
example, in a case where the luminescent center element is Eu.
[0108] As the sintering aid, at least one selected from the group
consisting of rare earth oxides, alkaline earth metal oxides,
aluminum oxide, aluminum nitride, silicon oxide, and hafnium oxide
is used, but it is preferable to use a combination of aluminum
nitride (AlN) and calcium carbonate (CaCO.sub.3).
[0109] The mixing ratio of the above-described raw material powder
is appropriately adjusted according to the fluorescence and light
transmitting properties of the target transparent fluorescent
sialon ceramic.
[0110] Next, a dispersant is added to the raw material powder and
wet mixing is performed in ethanol using a ball mill, thereby
preparing a slurry containing raw material powder.
[0111] Subsequently, the obtained slurry is heated using a heater
such as a mantle heater and ethanol contained in the slurry is
sufficiently evaporated, thereby obtaining a mixture of raw
material powder (mixed powder).
[0112] Next, two or more sieves with meshes having sizes different
from each other are used in a stepwise manner, the above-described
mixed powder is forcedly passed through these sieves, and the mixed
powder having a predetermined particle diameter is granulated.
[0113] Subsequently, a sufficiently melted binder such as paraffin,
a lubricant such as bis(2-ethylhexyl)phthalate, and a solvent such
as cyclohexane are sufficiently stirred and mixed with each other,
thereby preparing a binder solution.
[0114] Next, the granulated mixed powder is added to the binder
solution, the binder solution is mixed into the entire mixed powder
such that the binder solution permeates into the entire mixed
powder, the mixture is heated, and then the solvent is
evaporated.
[0115] Subsequently, after the solvent is sufficiently evaporated,
the mixed powder is forcedly passed through a sieve with meshes
having a predetermined size and then granulated powder having a
predetermined particle diameter is obtained.
[0116] Next, a predetermined amount of granulated powder is
collected such that the thickness of a molded body after molding
using a mold becomes a predetermined size and then the granulated
powder is supplied into the mold.
[0117] Subsequently, uniaxial press molding is performed at a
pressure of 50 MPa for 30 seconds using a uniaxial press molding
machine, thereby obtaining a primary molded body.
[0118] Next, the obtained primary molded body is chamfered and
packed in a vacuum pack.
[0119] Subsequently, the primary molded body packed in a vacuum
pack is molded by cold isostatic pressing (CIP) once or repeatedly
ten times at a pressure of 200 MPa for 1 minute using a cold
isostatic pressing device, thereby obtaining a secondary molded
body.
[0120] Next, the secondary molded body is placed on an alumina
boat, heated in an air stream of 70 L/min using an annular
resistance furnace, and degreased, and a binder included in the
secondary molded body is removed. In the degreasing process, the
heating temperature and the heating time of the secondary molded
body are set in two stages. In the first stage of heating, the
heating temperature is set to 500.degree. C. and the heating time
is set to 3 hours. In the second stage of heating, the heating
temperature is set to 560.degree. C. and the heating time is set to
3 hours.
[0121] Moreover, in order to promote evaporation of a binder or a
lubricant included in the secondary molded body to some extent or
to prevent carbon from remaining due to thermal decomposition of
the binder or the lubricant, it is preferable that the heating
temperature of the secondary molded body is set to be in a range of
300.degree. C. to 600.degree. C. and the heating time thereof is
set to be in a range of 1 hour to 10 hours.
[0122] Next, the degreased secondary molded body is pre-sintered in
a nitrogen atmosphere using a multi-purpose high-temperature
sintering furnace, thereby obtaining a sintered body.
[0123] In order to sinter the secondary molded body, a porous
crucible made of Si.sub.3N.sub.4, which is prepared by reaction
sintering, is disposed in a housing made of carbon, a porous column
plate made of Si.sub.3N.sub.4 is disposed in the crucible, and the
secondary molded body is disposed in the column plate shape.
[0124] In this sintering process, the temperature is increased at
20.degree. C./min in a vacuum (6.7.times.10.sup.-2 Pa or less) in a
temperature range of room temperature to 1200.degree. C., the
secondary molded body is pressed by nitrogen gas up to 0.25 MPa at
1200.degree. C. and pressed with a nitrogen gas flow of 4 L/min up
to 0.9 MPa while the temperature is increased at 10.degree. C./min
until the temperature reaches the target sintering temperature from
1200.degree. C. The sintering temperature of the secondary molded
body is set to 1600.degree. C. and the sintering time is set to 2
hours. Further, the pressure at the time of sintering is set to be
in a range of 0.88 MPa to 0.91 MPa in a nitrogen atmosphere.
[0125] Next, after the sintering is finished, the sintered body is
left to be naturally cooled to room temperature and then
cooled.
[0126] Subsequently, the sintered body is subjected to a
pressure-sintering treatment at a pressure of 50 MPa to 200 MPa and
a temperature of 1600.degree. C. to 1800.degree. C. for 1 hour in a
nitrogen atmosphere using a hot isostatic pressing (HIP)
device.
[0127] In this manner, the transparent fluorescent sialon ceramic
of the present embodiment is obtained.
[0128] According to the method of producing the transparent
fluorescent sialon ceramic of the present embodiment, it is
possible to remove a region having a different refractive index and
serving as a source of scattered light and a glass phase serving as
a light absorbing source by performing a process of preparing a
secondary molded body by cold isostatic press molding of the
primary molded body; a process of preparing a sintered body by
pre-sintering the secondary molded body in a nitrogen atmosphere;
and a process of performing a pressure-sintering treatment on the
sintered body in a nitrogen atmosphere. As a result, since the
sialon phosphor is uniformly present throughout the entire obtained
transparent fluorescent sialon ceramic, fluorescence is emitted
uniformly without being biased and the transmittance of visible
light is uniform without being biased. Further, the transparent
fluorescent sialon ceramic has less pores or glass phases in the
inside and thus there is no degradation of transparency resulting
from the pores or the glass phases and light-transmitting
properties are excellent.
[0129] [Method of Producing Transparent Fluorescent Sialon
Ceramic]
[0130] The method of producing a transparent fluorescent sialon
ceramic of the present embodiment includes a process of performing
a pressure-sintering treatment on a mixture which contains at least
silicon nitride powder, a substance serving as a luminescent center
element source, and a sintering aid in a nitrogen atmosphere.
[0131] The method of producing the transparent fluorescent sialon
ceramic of the present embodiment is applied to a case where the
silicon nitride compound is a compound which is represented by the
formula M.sub.x(Si,Al).sub.y(N,O).sub.z (here, M represents at
least one selected from the group consisting of alkaline earth
metals and rare earth metals, 0.2.ltoreq.x/z.ltoreq.0.6, and
0.4.ltoreq.y/z.ltoreq.0.8) and has a crystal structure similar to a
wurtzite type crystal structure.
[0132] First, silicon nitride (Si.sub.3N.sub.4) powder, calcium
nitride (Ca.sub.3N.sub.2) powder, aluminum nitride (AlN) powder,
and a substance serving as a luminescent center element source are
weighed so as to have a predetermined mass ratio.
[0133] As the substance serving as a luminescent center element
source, europium (II) oxide (EuO), europium (III) oxide
(Eu.sub.2O.sub.3), or europium nitride (EuN) is used, for example,
in a case where the luminescent center element is Eu.
[0134] The mixing ratio of the above-described raw material powder
is appropriately adjusted according to the fluorescence and light
transmitting properties of the target transparent fluorescent
sialon ceramic.
[0135] Next, the raw material powder is dry-mixed using a ball mill
and, for example, a glass bottle is filled with the obtained mixed
powder. The operations of weighing, mixing and filling of the raw
material powder are all carried out in a glove box.
[0136] Subsequently, the mixed powder fills the bottle in a
graphitic type. During the sintering, in order to prevent graphite
from being mixed into the sample, a boron nitride plate is
interposed between a punch bar of graphite and the sample.
[0137] Next, the mixture in the graphitic type is subjected to a
pulse conduction pressure-sintering treatment in a nitrogen
atmosphere.
[0138] The pulse conduction pressure-sintering treatment is carried
out under the conditions in a temperature range of 1600.degree. C.
to 1800.degree. C. at a pressure of 10 MPa to 200 MPa for a holding
time of 1 minute to 60 minutes.
[0139] In this manner, the transparent fluorescent sialon ceramic
of the present embodiment is obtained.
[0140] According to the method of producing the transparent
fluorescent sialon ceramic of the present embodiment, it is
possible to remove a region having a different refractive index and
serving as a light scattering source and a glass phase serving as a
light absorbing source by performing a process of performing a
pulse conduction pressure-sintering treatment on the mixture which
contains at least silicon nitride powder, a substance serving as a
luminescent center element source, and a sintering aid in a
nitrogen atmosphere. As a result, since the sialon phosphor is
uniformly present throughout the entire obtained transparent
fluorescent sialon ceramic, fluorescence is emitted uniformly
without being biased and the transmittance of visible light is
uniform without being biased. Further, the transparent fluorescent
sialon ceramic has less pores or glass phases in the inside and
thus there is no degradation of transparency resulting from the
pores or the glass phases and light-transmitting properties are
excellent.
[0141] The transparent fluorescent sialon ceramic of the present
embodiment can be applied to light emitting devices such as a light
emitting diode (LED), a fluorescent lamp, and a scintillator;
display devices such as a television and a display device for a
personal computer; and sensors.
[0142] In the related art, since a phosphor is supplied in a powder
form, it was difficult to apply a phosphor to a field in which a
single crystal is used such as a scintillator. However, the
transparent fluorescent sialon ceramic of the present embodiment is
a sintered body that forms any shape and thus can be widely applied
to the field in which a single crystal is used.
[0143] Moreover, a YAG transparent phosphor bulk body of the
related art has a problem in the temperature characteristic. That
is, it is reported that emission intensity of the YAG transparent
phosphor bulk body is decreased with an increase in temperature. On
the contrary, in the case of the transparent fluorescent sialon
ceramic of the present embodiment, quenching caused by an increase
of temperature is extremely small. That is, a light emitting device
with excellent color rendering properties or the like can be
realized using the transparent fluorescent sialon ceramic of the
present embodiment.
EXAMPLES
[0144] Hereinafter, the present invention will be described in more
detail with reference to experiment examples, but the present
invention is not limited to the following experiment examples.
Experiment Example 1
Production of Transparent Fluorescent Sialon Ceramic
[0145] First, silicon nitride (Si.sub.3N.sub.4) powder (trade name:
SN-E10, manufactured by UBE INDUSTRIES, LTD., purity >98%,
average particle diameter: 0.6 .mu.m), aluminum oxide
(Al.sub.2O.sub.3) powder (trade name: AKP-30, manufactured by
Sumitomo Chemical Company, Ltd.), aluminum nitride (AlN) powder
(manufactured by Tokuyama Corporation, F grade, purity >98%,
average particle diameter: 1.29 .mu.m), europium (III) oxide
(Eu.sub.2O.sub.3) (manufactured by Shin-Etsu Chemical Co., Ltd.),
yttrium (III) oxide (Y.sub.2O.sub.3) (trade name: RU-P,
manufactured by Shin-Etsu Chemical Co., Ltd., purity >99.9%,
average particle diameter: 1.1 .mu.m), and hafnium oxide
(HfO.sub.2) (trade name: HFE01PB, manufactured by KOJUNDO CHEMICAL
LABORATORY CO., LTD.) were weighed so as to have a mass ratio of
92:1.5:2.5:1:2.5:5
(=Si.sub.3N.sub.4:Al.sub.2O.sub.3:AlN:Eu.sub.2O.sub.3:Y.sub.2O.sub.3:HfO.-
sub.2).
[0146] Next, 2% by mass of a dispersant (trade name: SERNA E503,
manufactured by CHUKYO YUSHI CO., LTD., polyacrylic acid) was added
to the total amount of the raw material powder, wet mixing was
performed in ethanol at a rotation speed of 110 rpm for 48 hours
using a ball mill (pot: made of silicon nitride, internal volume:
400 mL, sialon ball: particle diameter of 5 mm, 1400 pieces),
thereby preparing a slurry containing raw material powder.
[0147] Subsequently, the obtained slurry was heated using a heater
such as a mantle heater and ethanol contained in the slurry was
sufficiently evaporated, thereby obtaining a mixture of raw
material powder (mixed powder).
[0148] Next, a sieve of #32 (nominal dimension: 500 .mu.m) and a
sieve of #48 (nominal dimension: 300 .mu.m) were used in this
order, the above-described mixed powder was forcedly passed through
these sieves, and the mixed powder having a predetermined particle
diameter was granulated.
[0149] Subsequently, sufficiently melted paraffin (manufactured by
Junsei Chemical Co., Ltd., melting point of 46.degree. C. to
48.degree. C.) as a binder, bis(2-ethylhexyl)phthalate
(manufactured by Wako Pure Chemical Industries, Ltd., purity of
97.0%) as a lubricant, and cyclohexane (manufactured by Wako Pure
Chemical Industries, Ltd., purity of 99.5%) as a solvent were
sufficiently stirred and mixed with each other, thereby preparing a
binder solution. Here, the amount of paraffin to be added was set
to 4% by mass and the amount of bis(2-ethylhexyl)phthalate to be
added was set to 2% by mass with respect to the total amount of raw
material powder. Further, the amount of cyclohexane to be added was
set to 35 mL/100 g.
[0150] Next, the granulated mixed powder was added to the binder
solution, the binder solution was mixed into the entire mixed
powder such that the binder solution permeated into the entire
mixed powder, the mixture was heated, and then the solvent was
evaporated.
[0151] Subsequently, after the solvent was sufficiently evaporated,
the mixed powder was forcedly passed through a sieve of #60
(nominal dimension: 250 .mu.m) and then granulated powder having a
predetermined particle diameter was obtained.
[0152] Next, 0.7 g of granulated powder was collected such that the
thickness of a molded body after molding using a stainless steel
mold in a cylindrical shape having a diameter of 15 mm became 2 mm
and then the granulated powder was supplied into the mold.
[0153] Subsequently, uniaxial press molding was performed at a
pressure of 500 MPa for 30 seconds using a uniaxial press molding
machine (trade name: MP-500H, manufactured by MARUTO INSTRUMENT
CO., LTD.), thereby obtaining a primary molded body.
[0154] Next, the obtained primary molded body was chamfered and
packed in a vacuum pack.
[0155] Subsequently, the primary molded body packed in a vacuum
pack was molded by cold isostatic pressing once or repeatedly ten
times at a pressure of 200 MPa for 60 seconds using a cold
isostatic pressing device (trade name: SE-HANDY CIP50-2000,
manufactured by Applied Power Japan, Ltd.), thereby obtaining a
secondary molded body.
[0156] Next, the secondary molded body was placed on an alumina
boat, heated in an air stream of 70 L/min using a tabular
resistance furnace, and degreased, and a binder included in the
secondary molded body was removed. In the degreasing process,
heating was carried out at 500.degree. C. for 3 hours and heating
was carried out at 560.degree. C. for 3 hours.
[0157] Moreover, in order to promote evaporation of a binder or a
lubricant included in the secondary molded body to some extent or
to prevent carbon from remaining due to thermal decomposition of
the binder or the lubricant, the secondary molded body was heated
at 250.degree. C. for 3 hours.
[0158] Next, the degreased secondary molded body was pre-sintered
in a nitrogen atmosphere using a multi-purpose high-temperature
sintering furnace (trade name: HIGH MULTI 5000, manufactured by
Fujidempa Kogyo Co., Ltd.), thereby obtaining a sintered body.
[0159] In order to sinter the secondary molded body, a porous
crucible made of Si.sub.3N.sub.4, which was prepared by reaction
sintering, was disposed in a housing made of carbon, a porous
column plate made of Si.sub.3N.sub.4 was disposed in the crucible,
and the secondary molded body was disposed on the column plate.
[0160] In this sintering process, the temperature was increased at
20.degree. C./min in a vacuum (6.7.times.10.sup.-2 Pa or less) in a
temperature range of room temperature to 1200.degree. C., the
secondary molded body was pressed by nitrogen gas up to 0.25 MPa at
1200.degree. C. and pressed with a nitrogen gas flow of 4 L/min up
to 0.9 MPa while the temperature was increased at 10.degree. C./min
from 1200.degree. C. to 1600.degree. C. The sintering temperature
of the secondary molded body was set to 1600.degree. C. and the
sintering time was set to 2 hours. Further, the pressure at the
time of sintering was set to be in a range of 0.88 to 0.91 MPa in a
nitrogen atmosphere.
[0161] Next, after the sintering was finished, the sintered body
was left to be naturally cooled to room temperature and then
cooled.
[0162] Subsequently, the sintered body was subjected to a
pressure-sintering treatment at 100 MPa and 1700.degree. C. for 1
hour in a nitrogen atmosphere using a hot isostatic pressing
processing device (trade name: SYSTEM15X, manufactured by KOBE
STEEL LTD.), thereby obtaining a transparent fluorescent sialon
ceramic of Experiment Example 1.
[0163] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 1 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 1 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0164] (Measurement of Transmittance)
[0165] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 1, the linear transmittance of visible light
was measured.
[0166] The transmittance of visible light was measured by fixing a
sample having a thickness of 100 .mu.m to a jig with tape and
setting the measurement wavelength region to be in a range of 300
nm to 800 nm using LAMBDA 750 (manufactured by Perkin Elmer Co.,
Ltd.). The results are shown in Table 1 and FIG. 1.
[0167] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0168] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 1, the emission spectrum and the excitation
spectrum were measured.
[0169] In measurement of the emission spectrum and the excitation
spectrum, the measurement wavelength region was set such that the
emission spectrum was excited at 405 nm and was in a range of 430
nm to 700 nm and the excitation spectrum was excited at 540 nm and
was in a range of 280 nm to 500 nm (under a 270 nm cut-off filter)
using FP6300 (manufactured by Jasco Corporation). The results
thereof are shown in FIG. 2.
Experiment Example 2
Production of Transparent Fluorescent Sialon Ceramic
[0170] A transparent fluorescent sialon ceramic of Experiment
Example 2 was obtained in the same manner as in Experiment Example
1 except that silicon nitride (Si.sub.3N.sub.4) powder, aluminum
oxide (Al.sub.2O.sub.3) powder, aluminum nitride (AlN) powder,
europium (III) oxide (Eu.sub.2O.sub.3), yttrium (III) oxide
(Y.sub.2O.sub.3), and hafnium oxide (HfO.sub.2) were weighed so as
to have a mass ratio of 92:1.5:3.5:1:2.5:5
(=Si.sub.3N.sub.4:Al.sub.2O.sub.3:AlN:Eu.sub.2O.sub.3:Y.sub.2O.sub.3:HfO.-
sub.2).
[0171] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 2 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 2 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0172] (Measurement of Transmittance)
[0173] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 2, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1 and FIG. 1.
[0174] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0175] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 2, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The results thereof are shown in FIG. 3.
Experiment Example 3
Production of Transparent Fluorescent Sialon Ceramic
[0176] A transparent fluorescent sialon ceramic of Experiment
Example 3 was obtained in the same manner as in Experiment Example
1 except that silicon nitride (Si.sub.3N.sub.4) powder, aluminum
oxide (Al.sub.2O.sub.3) powder, aluminum nitride (AlN) powder,
europium (III) oxide (Eu.sub.2O.sub.3), yttrium (III) oxide
(Y.sub.2O.sub.3), and hafnium oxide (HfO.sub.2) were weighed so as
to have a mass ratio of 92:1.5:5:1:2.5:5
(=Si.sub.3N.sub.4:Al.sub.2O.sub.3:AlN:Eu.sub.2O.sub.3:Y.sub.2O.sub.3:HfO.-
sub.2).
[0177] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 3 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 3 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0178] (Measurement of Transmittance)
[0179] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 3, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in FIG. 1.
[0180] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0181] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 3, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The results thereof are shown in FIG. 4.
Experiment Example 4
Production of Transparent Fluorescent Sialon Ceramic
[0182] A transparent fluorescent sialon ceramic of Experiment
Example 4 was obtained in the same manner as in Experiment Example
1 except that silicon nitride (Si.sub.3N.sub.4) powder, aluminum
oxide (Al.sub.2O.sub.3) powder, aluminum nitride (AlN) powder,
europium (III) oxide (Eu.sub.2O.sub.3), yttrium (III) oxide
(Y.sub.2O.sub.3), and hafnium oxide (HfO.sub.2) were weighed so as
to have a mass ratio of 92:1.5:1.5:1:2.5:5
(=Si.sub.3N.sub.4:Al.sub.2O.sub.3:AlN:Eu.sub.2O.sub.3:Y.sub.2O.sub.3:HfO.-
sub.2).
[0183] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 4 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 4 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0184] (Measurement of Transmittance)
[0185] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 4, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in FIG. 1.
[0186] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0187] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 4, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The results thereof are shown in FIG. 5.
Experiment Example 5
Production of Transparent Fluorescent Sialon Ceramic
[0188] First, silicon nitride (Si.sub.3N.sub.4) powder (trade name:
SN-E10, manufactured by UBE INDUSTRIES, LTD., purity >98%,
average particle diameter: 0.6 .mu.m), aluminum nitride (AlN)
powder (manufactured by Tokuyama Corporation, F grade, purity
>98%, average particle diameter: 1.29 .mu.m), cerium (IV) oxide
(CeO.sub.2) (manufactured by Shin-Etsu Chemical Co., Ltd.), and
yttrium (III) oxide (Y.sub.2O.sub.3) (trade name: RU-P,
manufactured by Shin-Etsu Chemical Co., Ltd., purity >99.9%,
average particle diameter: 1.1 .mu.m) were weighed so as to have a
molar ratio of 21:9:0.2:0.9
(=Si.sub.3N.sub.4:AlN:CeO.sub.2:Y.sub.2O.sub.3).
[0189] Next, 2% by mass of a dispersant (trade name: SERNA E503,
manufactured by CHUKYO YUSHI CO., LTD., polyacrylic acid) was added
to the total amount of the raw material powder, wet mixing was
performed in ethanol at a rotation speed of 110 rpm for 48 hours
using a ball mill (pot: made of silicon nitride, internal volume:
400 mL, sialon ball: particle diameter of 5 mm, 1400 pieces),
thereby preparing a slurry containing raw material powder.
[0190] Subsequently, the obtained slurry was heated using a heater
such as a mantle heater and ethanol contained in the slurry was
sufficiently evaporated, thereby obtaining a mixture of raw
material powder (mixed powder).
[0191] Next, a sieve of #32 (nominal dimension: 500 nm) and a sieve
of #48 (nominal dimension: 300 nm) were used in this order, the
above-described mixed powder was forcedly passed through these
sieves, and the mixed powder having a predetermined particle
diameter was granulated.
[0192] Subsequently, sufficiently melted paraffin (manufactured by
Junsei Chemical Co., Ltd., melting point of 46.degree. C. to
48.degree. C.) as a binder, bis(2-ethylhexyl)phthalate
(manufactured by Wako Pure Chemical Industries, Ltd., purity of
97.0%) as a lubricant, and cyclohexane (manufactured by Wako Pure
Chemical Industries, Ltd., purity of 99.5%) as a solvent were
sufficiently stirred and mixed with each other, thereby preparing a
binder solution. Here, the amount of paraffin to be added was set
to 4% by mass and the amount of bis(2-ethylhexyl)phthalate to be
added was set to 2% by mass with respect to the total amount of raw
material powder. Further, the amount of cyclohexane to be added was
set to 35 mL/100 g.
[0193] Next, the granulated mixed powder was added to the binder
solution, the binder solution was mixed into the entire mixed
powder such that the binder solution permeated into the entire
mixed powder, the mixture was heated, and then the solvent was
evaporated.
[0194] Subsequently, after the solvent was sufficiently evaporated,
the mixed powder was forcedly passed through a sieve of #60
(nominal dimension: 250 nm) and then granulated powder having a
predetermined particle diameter was obtained.
[0195] Next, 0.7 g of granulated powder was collected such that the
thickness of a molded body after molding using a stainless steel
mold in a cylindrical shape having a diameter of 15 mm became 2 mm
and then the granulated powder was supplied into the mold.
[0196] Subsequently, uniaxial press molding was performed at a
pressure of 500 MPa for 30 seconds using a uniaxial press molding
machine (trade name: MP-500H, manufactured by MARUTO INSTRUMENT
CO., LTD.), thereby obtaining a primary molded body.
[0197] Next, the obtained primary molded body was chamfered and
packed in a vacuum pack.
[0198] Subsequently, the primary molded body packed in a vacuum
pack was molded by cold isostatic pressing once at a pressure of
200 MPa for 60 seconds using a cold isostatic pressing device
(trade name: SE-HANDY CIP50-2000, manufactured by Applied Power
Japan, Ltd.), thereby obtaining a secondary molded body.
[0199] Next, the secondary molded body was placed on an alumina
boat, heated in an air stream of 70 L/min using a tabular
resistance furnace, and degreased, and a binder included in the
secondary molded body was removed. In the degreasing process,
heating was carried out at 500.degree. C. for 3 hours and heating
was carried out at 560.degree. C. for 3 hours.
[0200] Moreover, in order to promote evaporation of a binder or a
lubricant included in the secondary molded body to some extent or
to prevent carbon from remaining due to thermal decomposition of
the binder or the lubricant, the secondary molded body was heated
at 250.degree. C. for 3 hours.
[0201] Next, the degreased secondary molded body was pre-sintered
in a nitrogen atmosphere using a multi-purpose high-temperature
sintering furnace (trade name: HIGH MULTI 5000, manufactured by
Fujidempa Kogyo Co., Ltd.), thereby obtaining a sintered body.
[0202] In order to sinter the secondary molded body, a porous
crucible made of Si.sub.3N.sub.4, which was prepared by reaction
sintering, was disposed in a housing made of carbon, a porous
column plate made of Si.sub.3N.sub.4 was disposed in the crucible,
and the secondary molded body was disposed on the column plate.
[0203] In this sintering process, the temperature was increased at
20.degree. C./min in a vacuum (6.7.times.10.sup.-2 Pa or less) in a
temperature range of room temperature to 1200.degree. C., the
secondary molded body was pressed by nitrogen gas up to 0.25 MPa at
1200.degree. C. and pressed with a nitrogen gas flow of 4 L/min up
to 0.9 MPa while the temperature was increased at 10.degree. C./min
from 1200.degree. C. to 1600.degree. C. The sintering temperature
of the secondary molded body was set to 1600.degree. C. and the
sintering time was set to 2 hours. Further, the pressure at the
time of sintering was set to be in a range of 0.88 to 0.91 MPa in a
nitrogen atmosphere.
[0204] Next, after the sintering was finished, the sintered body
was left to be naturally cooled to room temperature and then
cooled.
[0205] Subsequently, the sintered body was subjected to a
pressure-sintering treatment at 100 MPa and 1600.degree. C. for 1
hour in a nitrogen atmosphere using a hot isostatic pressing
processing device (trade name: SYSTEM15X, manufactured by KOBE
STEEL LTD.), thereby obtaining a transparent fluorescent sialon
ceramic of Experiment Example 5.
[0206] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 5 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 5 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0207] (Measurement of Transmittance)
[0208] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 5, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1 and FIG. 6.
[0209] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0210] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 5, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement results of the emission wavelength peak and the
excitation wavelength peak are listed in Table 1.
Experiment Example 6
Production of Transparent Fluorescent Sialon Ceramic
[0211] A transparent fluorescent sialon ceramic of Experiment
Example 6 was obtained in the same manner as in Experiment Example
5 except that a secondary molded body was obtained by performing
cold isostatic press molding ten times.
[0212] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 6 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 6 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0213] (Measurement of Transmittance)
[0214] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 6, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1 and FIG. 6.
[0215] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0216] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 6, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement results of the emission wavelength peak and the
excitation wavelength peak are shown in Table 1.
Experiment Example 7
Production of Transparent Fluorescent Sialon Ceramic
[0217] A transparent fluorescent sialon ceramic of Experiment
Example 7 was obtained in the same manner as in Experiment Example
5 except that phenolic resin spherical powder (trade name: R800,
average particle diameter: 20 to 50 .mu.m, manufactured by AIR
WATER INC.) was added as a pore-forming agent such that the mass
ratio between the phenolic resin spherical powder and silicon
nitride (Si.sub.3N.sub.4) powder which was one of the sialon raw
material powder became 92:3.
[0218] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 7 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 7 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0219] (Measurement of Transmittance)
[0220] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 7, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1 and FIG. 6.
[0221] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0222] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 7, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement results of the emission wavelength peak and the
excitation wavelength peak are shown in Table 1.
Experiment Example 8
Production of Transparent Fluorescent Sialon Ceramic
[0223] A transparent fluorescent sialon ceramic of Experiment
Example 8 was obtained in the same manner as in Experiment Example
7 except that a secondary molded body was obtained by cold
isostatic press molding ten times.
[0224] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 8 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 8 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0225] (Measurement of Transmittance)
[0226] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 8, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1 and FIG. 6.
[0227] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0228] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 8, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement results of the emission wavelength peak and the
excitation wavelength peak are shown in Table 1.
Experiment Example 9
Production of Transparent Fluorescent Sialon Ceramic
[0229] A transparent fluorescent sialon ceramic of Experiment
Example 9 was obtained in the same manner as in Experiment Example
5 except that phenolic resin spherical powder was added as a
pore-forming agent such that the mass ratio between the phenolic
resin spherical powder and silicon nitride (Si.sub.3N.sub.4) powder
which was one of the sialon raw material powder became 92:5.
[0230] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 9 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 9 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0231] (Measurement of Transmittance)
[0232] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 9, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in FIG. 6.
[0233] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0234] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 9, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement results of the emission wavelength peak and the
excitation wavelength peak are shown in Table 1.
Experiment Example 10
Production of Transparent Fluorescent Sialon Ceramic
[0235] A transparent fluorescent sialon ceramic of Experiment
Example 10 was obtained in the same manner as in Experiment Example
5 except that silicon nitride (Si.sub.3N.sub.4) powder, aluminum
nitride (AlN) powder, cerium (IV) oxide (CeO.sub.2), and yttrium
(III) oxide (Y.sub.2O.sub.3) were weighed so as to have a molar
ratio of 21:9:0.5:1 (=Si.sub.3N.sub.4:AlN:CeO.sub.2:Y.sub.2O.sub.3)
and performing cold isostatic press molding ten times, thereby
obtaining a secondary molded body.
[0236] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 10 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 10 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0237] (Measurement of Transmittance)
[0238] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 10, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1.
[0239] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0240] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 10, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement result of the emission spectrum is shown in FIG.
7 and the measurement result of the excitation spectrum is shown in
FIG. 8.
[0241] Further, the measurement results of the emission wavelength
peak and the excitation wavelength peak are shown in Table 1.
Experiment Example 11
Production of Transparent Fluorescent Sialon Ceramic
[0242] First, silicon nitride (Si.sub.3N.sub.4) powder (trade name:
SN-E10, manufactured by UBE INDUSTRIES, LTD., purity >98%,
average particle diameter: 0.6 .mu.m), aluminum nitride (AlN)
powder (manufactured by Tokuyama Corporation, F grade, purity
>98%, average particle diameter: 1.29 .mu.m), yttrium (III)
oxide (Y.sub.2O.sub.3) (trade name: RU-P, manufactured by Shin-Etsu
Chemical Co., Ltd., purity >99.9%, average particle diameter:
1.1 .mu.m), and europium (III) oxide (Eu.sub.2O.sub.3)
(manufactured by Shin-Etsu Chemical Co., Ltd.) were weighed so as
to have a molar ratio of 21:9:0.9:0.1
(=Si.sub.3N.sub.4:AlN:Y.sub.2O.sub.3:Eu.sub.2O.sub.3).
[0243] Next, 2% by mass of a dispersant (trade name: SERNA E503,
manufactured by CHUKYO YUSHI CO., LTD., polyacrylic acid) was added
to the total amount of the raw material powder, wet mixing was
performed in ethanol at a rotation speed of 110 rpm for 48 hours
using a ball mill (pot: made of polystyrene, internal volume: 250
mL, sialon ball: particle diameter of 5 mm, 700 pieces), thereby
preparing a slurry containing raw material powder.
[0244] Subsequently, the obtained slurry was heated using a heater
such as a mantle heater and ethanol contained in the slurry was
sufficiently evaporated, thereby obtaining a mixture of raw
material powder (mixed powder).
[0245] Next, a sieve of #32 (nominal dimension: 500 .mu.m) and a
sieve of #48 (nominal dimension: 300 .mu.m) were used in this
order, the above-described mixed powder was forcedly passed through
these sieves, and the mixed powder having a predetermined particle
diameter was granulated.
[0246] Subsequently, sufficiently melted paraffin (manufactured by
Junsei Chemical Co., Ltd., melting point of 46.degree. C. to
48.degree. C.) as a binder, bis(2-ethylhexyl)phthalate
(manufactured by Wako Pure Chemical Industries, Ltd., purity of
97.0%) as a lubricant, and cyclohexane (manufactured by Wako Pure
Chemical Industries, Ltd., purity of 99.5%) as a solvent were
sufficiently stirred and mixed with each other, thereby preparing a
binder solution. Here, the amount of paraffin to be added was set
to 4% by mass and the amount of bis(2-ethylhexyl)phthalate to be
added was set to 2% by mass with respect to the total amount of raw
material powder. Further, the amount of cyclohexane to be added was
set to 35 mL/100 g.
[0247] Next, the granulated mixed powder was added to the binder
solution, the binder solution was mixed into the entire mixed
powder such that the binder solution permeated into the entire
mixed powder, the mixture was heated, and then the solvent was
evaporated.
[0248] Subsequently, after the solvent was sufficiently evaporated,
the mixed powder was forcedly passed through a sieve of #60
(nominal dimension: 250 .mu.m) and then granulated powder having a
predetermined particle diameter was obtained.
[0249] Next, 0.7 g of granulated powder was collected such that the
thickness of a molded body after molding using a stainless steel
mold in a cylindrical shape having a diameter of 15 mm became 2 mm
and then the granulated powder was supplied into the mold.
[0250] Subsequently, uniaxial press molding was performed at a
pressure of 500 MPa for 30 seconds using a uniaxial press molding
machine (trade name: MP-500H, manufactured by MARUTO INSTRUMENT
CO., LTD.), thereby obtaining a primary molded body.
[0251] Next, the obtained primary molded body was chamfered and
packed in a vacuum pack.
[0252] Subsequently, the primary molded body packed in a vacuum
pack was molded by repeatedly performing cold isostatic pressing
ten times at a pressure of 200 MPa for 60 seconds using a cold
isostatic pressing device (trade name: SE-HANDY CIP50-2000,
manufactured by Applied Power Japan, Ltd.), thereby obtaining a
secondary molded body.
[0253] Next, the secondary molded body was placed on an alumina
boat, heated in an air stream of 70 L/min using a tabular
resistance furnace, and degreased, and a binder included in the
secondary molded body was removed. In the degreasing process,
heating was carried out at 500.degree. C. for 3 hours.
[0254] Moreover, in order to promote evaporation of a binder or a
lubricant included in the secondary molded body to some extent or
to prevent carbon from remaining due to thermal decomposition of
the binder or the lubricant, the secondary molded body was heated
at 250.degree. C. for 3 hours.
[0255] Next, the degreased secondary molded body was pre-sintered
in a nitrogen atmosphere using a multi-purpose high-temperature
sintering furnace (trade name: HIGH MULTI 5000, manufactured by
Fujidempa Kogyo Co., Ltd.), thereby obtaining a sintered body.
[0256] In order to sinter the secondary molded body, a porous
crucible made of Si.sub.3N.sub.4, which was prepared by reaction
sintering, was disposed in a housing made of carbon, a porous
column plate made of Si.sub.3N.sub.4 was disposed in the crucible,
and the secondary molded body was disposed on the column plate.
[0257] In this sintering process, the temperature was increased at
20.degree. C./min in a vacuum (6.7.times.10-2 Pa or less) in a
temperature range of room temperature to 1200.degree. C., the
secondary molded body was pressed by nitrogen gas up to 0.25 MPa at
1200.degree. C. and pressed with a nitrogen gas flow of 4 L/min up
to 0.9 MPa while the temperature was increased at 10.degree. C./min
from 1200.degree. C. to 1600.degree. C. The sintered body prepared
by setting the sintering temperature of the secondary molded body
to 1700.degree. C. and the sintering condition to 2 hours was left
to be naturally cooled to room temperature and then cooled after
the sintering was finished. Subsequently, the sintered body was
subjected to a pressure-sintering treatment at 100 MPa and
1600.degree. C. for 1 hour in a nitrogen atmosphere using a hot
isostatic pressing processing device (trade name: SYSTEM15X,
manufactured by KOBE STEEL LTD.), thereby obtaining a transparent
fluorescent sialon ceramic of Experiment Example 11.
[0258] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 11 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 11 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0259] (Measurement of Transmittance)
[0260] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 11, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1.
[0261] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0262] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 11, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement results of the emission wavelength peak and the
excitation wavelength peak are listed in Table 1.
Experiment Example 12
Production of Transparent Fluorescent Sialon Ceramic
[0263] A transparent fluorescent sialon ceramic of Experiment
Example 12 was obtained in the same manner as in Experiment Example
11 except that silicon nitride (Si.sub.3N.sub.4) powder (trade
name: SN-E10, manufactured by UBE INDUSTRIES, LTD., purity >98%,
average particle diameter: 0.6 .mu.m), aluminum nitride (AlN)
powder (manufactured by Tokuyama Corporation, F grade, purity
>98%, average particle diameter: 1.29 .mu.m), yttrium (III)
oxide (Y.sub.2O.sub.3) (trade name: RU-P, manufactured by Shin-Etsu
Chemical Co., Ltd., purity >99.9%, average particle diameter:
1.1 .mu.m), CaCO.sub.3 (manufactured by Junsei Chemical Co., Ltd.),
and europium (III) oxide (Eu.sub.2O.sub.3) (manufactured by
Shin-Etsu Chemical Co., Ltd) were weighed so as to have a molar
ratio of 21:9:0.675:0.45:0.1
(=Si.sub.3N.sub.4:AlN:Y.sub.2O.sub.3:CaCO.sub.3:Eu.sub.2O.sub.3).
[0264] (Measurement of Transmittance)
[0265] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 12, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1.
[0266] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0267] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 12, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
1. The measurement results of the emission wavelength peak and the
excitation wavelength peak are shown in Table 1 and FIG. 9.
Experiment Example 13
Production of Transparent Fluorescent Sialon Ceramic
[0268] First, silicon nitride (Si.sub.3N.sub.4) powder (trade name:
SN-E10, manufactured by UBE INDUSTRIES, LTD., purity >98%,
average particle diameter: 0.6 .mu.m), aluminum nitride (AlN)
powder (manufactured by Tokuyama Corporation, H grade, purity
>98%, average particle diameter: 1.29 .mu.m), europium oxide
(III) (Eu.sub.2O.sub.3) (manufactured by Shin-Etsu Chemical Co.,
Ltd.), and calcium nitride (Ca.sub.3N.sub.2) (manufactured by
SIGMA-ALDLICH Corporation) were weighed so as to have a molar ratio
of 1:1:0.016:0.984 (=Si:Al:Eu:Ca).
[0269] Next, the raw material powder was dry-mixed using a ball
mill for 5 hours and a bottle was filled with the obtained mixed
powder. The operations of weighing, mixing and filling of the raw
material powder were all carried out in a glove box.
[0270] Subsequently, 3 g of the mixed powder fills the bottle in a
graphitic type having a diameter of 25 mm, and a BN plate was
interposed between a punch bar of graphite and a sample, uniaxially
pressed at 30 MPa, and fired using a spark plasma sintering device
(trade name: SPS-1050, manufactured by Fuji Electronic Industries
Co., Ltd.) to prepare a sintered body, thereby obtaining a
transparent fluorescent sialon ceramic of Experiment Example
13.
[0271] The sintering temperature was set to 1760.degree. C., the
sintering time was set to 10 minutes, and the sintering was carried
out in a nitrogen gas atmosphere.
[0272] The shape of the transparent fluorescent sialon ceramic of
Experiment Example 13 was columnar. Further, the transparent
fluorescent sialon ceramic of Experiment Example 12 was thinned by
machining and the final thickness thereof was set to 100 .mu.m.
When the thickness thereof was adjusted to be smaller, both-sided
mirror surface polishing was performed.
[0273] (Measurement of Transmittance)
[0274] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 13, the linear transmittance of visible light
was measured in the same manner as in Experiment Example 1. The
results are shown in Table 1.
[0275] (Measurement of Emission Spectrum and Excitation
Spectrum)
[0276] With respect to the transparent fluorescent sialon ceramic
of Experiment Example 13, the emission spectrum and the excitation
spectrum were measured in the same manner as in Experiment Example
12. In measurement of the emission spectrum and the excitation
spectrum, the measurement wavelength region was set such that the
emission spectrum was excited at 471 nm and was in a range of 485
nm to 750 nm and the excitation spectrum was excited at 633 nm and
was in a range of 220 nm to 600 nm using FP6300 (manufactured by
Jasco Corporation). The results thereof are shown in FIG. 10.
Further, the measurement results of the emission wavelength peak
and the excitation wavelength peak are listed in Table 1.
TABLE-US-00001 TABLE 1 Excitation Emission Linear Experiment
Thickness wavelength wavelength transmittance Example Compound name
[.mu.m] peak [nm] peak [nm] (800 nm) [%] 1 .beta.-SiAlON:Eu 100 313
535.5 11 2 .beta.-SiAlON:Eu 100 305.5 532 18 5 Y-.alpha.SiAlON:Ce
100 367.5 476.5 70 6 Y-.alpha.SiAlON:Ce 100 366.5 476.5 68 7
Y-.alpha.SiAlON:Ce 100 368.5 477.5 65 8 Y-.alpha.SiAlON:Ce 100
368.5 478.5 65 10 Y-.alpha.SiAlON:Ce 100 373.5 490.5 66 11
Y-.alpha.SiAlON:Eu 100 450 594 33 12 Ca,Y-.alpha.SiAlON:Eu 100 450
580 23 13 CaAlSiN.sub.3 100 471 633 19
[0277] As shown from the results of Table 1 and FIGS. 2, 3, and 4,
the transparent fluorescent sialon ceramics of Experiment Examples
1 to 4 are capable of emitting green fluorescent light. Further, as
shown from the results of Table 1 and FIGS. 5, 7, and 8, the
transparent fluorescent sialon ceramics of Experiment Examples 5 to
11 are capable of emitting blue to blue-green fluorescent light.
Further, as shown from the results of Table 1 and FIG. 9, the
transparent fluorescent sialon ceramics of Experiment Examples 11
and 12 are capable of emitting yellow fluorescent light.
Furthermore, as shown from the results of Table 1 and FIG. 10, the
transparent fluorescent sialon ceramic of Experiment Example 13 is
capable of emitting red fluorescent light.
[0278] From the results of FIG. 6, it was understood that the
transmittance of visible light in the transparent fluorescent
sialon ceramic is decreased when the amount of phenolic resin
spherical powder to be added as a pore-forming agent is increased.
It is considered that a decrease in transmittance is caused by fine
pores, formed in the transparent fluorescent sialon ceramic,
containing air due to addition of the phenolic resin spherical
powder as a pore-forming agent. Further, it was understood that a
difference in transmittance of visible light between the
transparent fluorescent sialon ceramic obtained through cold
isostatic press molding performed once and the transparent
fluorescent sialon ceramic obtained through cold isostatic press
molding performed ten times was not large.
[0279] Moreover, from the results of FIGS. 7 and 8, it was
understood that the emission wavelength and the excitation
wavelength in the transparent fluorescent sialon ceramic can be
shifted by changing the amount of cerium (IV) oxide (CeO.sub.2) to
be added.
INDUSTRIAL APPLICABILITY
[0280] According to the present invention, it is possible to mold a
transparent fluorescent sialon ceramic into a predetermined shape
with the form as it is and to apply the molded transparent
fluorescent sialon ceramic to a white LED. Further, it is not
necessary for a sialon phosphor to be dispersed in a resin for use
as in the related art, and it is possible to obtain a transparent
fluorescent sialon ceramic in which the luminous efficiency of a
white LED is not degraded due to scattering of light caused by a
difference in refractive index between a sialon phosphor and a
resin. Therefore, the present invention is extremely useful.
* * * * *